Drill grinding fixture



Oct. 30, 1956 E. c. CLARKE DRILL @BINDING FIXTURE 2 Sheets-Sheet l Filed April s, 1953 R. m5 m N EK, Y. V 3 oww/wm mm, lHI G G l, |.l| H F F ,I.. Ln.. o I f M W. Y m w 22% 2395 v FIG. vI?.

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Oct. 30, .1956 E. c. CLARKE 2,768,485

` DRILL GRINDING FIXTURE:

Filed April 3, 1953 2 Sheets-Sheet 2 OFFSET INVENTOR. EDMUND c. @Me/.17

ATTONE Y.

Unite States arent 2,768,485 Patented Get. 3G, i956 DRILL GRMDING FIXTURE Edmund C. Clarke, Grange Park, Fla. Application April 3, 1953, Serial No. 346,682

18 Claims. (Cl. SI1- 219) This invention relates to drill grinding fixtures and more particularly to a fixture of an adjustable nature to accommodate various sizes of drills and for grinding taper shank drills.

Among the objects of my invention are to provide a relatively simple and durable fixture having a high degree of versatility for grinding either ordinary or -taper lshank drills and for grinding them with a minimum of skill 'required on the part `of the operator. A further object of my invention is to provide a fixture whichwill accurately grind a drill point and which will automatically effect a motion of the drill being ground so as to differentially grind the point whereby more material is removed from the heels of the drill point than from the surface near the yweb so that suitable clearance is effected while at the same time a full bodydirectly back of each lip is maintained to strengthen it. Additional objects of my invention are :to furnish uniformity of grinding of the lips and also to lprovidethe proper angle between the lips and the drill web or point. Y

The present invention is a further developmentand improvement of the subject matter of my patent application S. N. 112,930, filed August 29, 1949, which issued as1Patent No. 7,723,510, dated November 15, 1955, for Drill Grinding Fixture Combination.

In brief, the present invention provides an eccentrically mounted drill holding cradle arranged for oscillatory movement and provided with cam elements which reciprocate the cradle bodily toward and away from thel grinding wheel simultaneously with oscillation. This combination of motion effects a differential grinding of the surface of the point so as to leave a desirableclearance for the respective lips. l also provide various means for positioning the drill point with respect to the grinding wheel whereby al predetermined angle of grinding engagement is effected so that the lips are ground at the proper angle with respect to the web. One such means consists ofa mirror with a scratch mark on it permanently secured in position Yadjacent the surface of the wheel, the scratch markbeing used to set the angle of the drill lip; another'means consisting of a mark on the drill holding cradle ldisposed in -a predetermined manner.

yMy invention also embraces an adjustable length cradle ,for holding a drill, in conjunction with a stop ymeans for positioning of the drill lips alternately forvengagement Ywith the grinding .Wheel in the manner set fonthtin my above-mentioned prior patent. Further a .portion of the cradle is adapted to take taper shank drills. Anieans for holding down kand steadying the drill point .during grinding is also provided.

The invention will now beldescribed in detail .in ,coujunction with the appended drawing in which:

Fig. l is ,an elevation of one side of my linvention lshow- Aing the fixture in position relative agrindingfwheel.

Fig. 4 Yis an elevatio-n of the front of the fixture.

Fig. 5 is a view in the direction 5-5 of Figure 1.

Fig. 6 isa plan view of the hold-down element.

Fig. 7 is a rear view of the adjustable portion of the cradle.

Fig. 8 is a bottom View taken in direction 8 8 of Fig. 7.

Fig. 9 is a modification of the adjustable portion of the cradle.

Fig. 10 shows a magnified drill point.

With reference to the drawing, my invention comprises a base 10 having an adjustable slidable plate 14 there being dovetail ways between the base 10 and plate 14 as shown. Plate 14 has lugs 16 and 18 having bores through which passes an adjusting screw 22 having an end carried in a lug 24 of base 10. Thus it will be understood that rotation of a nut 23 on the screw 22 will effect reciprocal motion of the plate 14 by virtue of abutment of nut 23 against either of lugs 16 and 13. A slidable plate 30 is carried by means of dovetail ways on the plate 14. A .spring 32 recessed for the most part in the plate 30 and abutting a flange 36 of plate 14 serves to bias plate 30 rearwardly, i. e., to the right as viewed on Figs. 1 and 2. On the opposite end of plate 14 a fiange 38 is formed having a top surface which carries a cam 46. The cam 4d is pivotally connected to the top surface of flange 3 8 by means of a pivot 44 and has aycam surface 46 and a slot 50 which accommodates a screw 52 passing through the slot and threaded in the plate 14. The screw 5 2 eX- tends through the thickness of plate 30 by virtue of an arcuate cut out 54 provided in that plate. Thus the cam may be adjusted Ito or fro about pivot 44 to any desired position and held in that position by means `of the screw 52. A limit screw 6i) is provided, having threaded en- .gagement in the flange 38 and abuttable against the arcuate surface 63, to limit rearward motion of plate 30.

An upright pin 64 is carried by the plate 30 in any suit- Vable manner and rotatably secured by the pin isa post 66 'havinga earn follower 67 which is engageable with cam -at the proper point on cam surface 46 prior to swinging post..66 counterclockwise. Thus, as the cam surfaceis adjusted by virtue of the screw and slot r arrangement 5ft-52, it may be necessary to readjust screw 60 so that the. follower and the cam surface 46 will be properly arranged with respect to each other.

At the upper end of the post is secured a pivot pin 72 to pivotally secure a front element 76 of a drill cradle.

The structure provides a conventional offset to the side .and forwardly as indicated by Offset in Figures 1 and 4. The angularity of element 76 may be adjusted to the standard angles of 49, 59, and 68 yby means of a removable vscrew 86 which is selectively engageable through bores y7-7 and 78 in post 66 with any one of three threaded holes `8,2,v 84, or 86 laid o ut as shown in element 76. Thus, an accurate and fixed setting for grinding any of the three standard langles may be rapidly and accurately effected.

Front element 76 carries by means of lug 90 a holddown member 94 pivotally supported by a pin 96 passing through lug-9i) and biased by means .of a spring 100. The hold-down member comprises a bracket 102 and a bottlelshaped 'roller 164 rotatably carried by means of a pin 106 supported in the bracket arms as shown in Fig. 6. The

Y outer end of the bracket yterminates in a small handle'108 which Amay be depressed to raise the roller Yor released to permit it to bear against a drill 112. The shape of the roller is to preclude its riding into the drill utes or bouncing on the lands.

Front element 76 has a square shaft 116 secured thereto on which is slidably mounted a carriage 118 consisting of a base member 120, secured slidably to shaft 116 by means of a clamp plate 122 bolted in place as shown in Figs. 5 and 8. Base member 129 has secured in the front face thereof a pair of studs l26a and '12611 for a purpose hereinafter described. The side of the base member has a holding screw 128 threadably carried therein which can be rotated to abut the side of shaft 116 for the purpose of holding the base member at any selected position thereon, depending on the length `of drill.

A drill holding element 132 is carried by means of dovetail ways, as shown, in the base element 120 and has a ange 134 which carries an adjusting screw 138 having its lower end threadably engaged in base 120. Thus rotation of the screw 138 serves to raise or lower the drill holder element 132 in a direction normal to shaft 116, depending upon the diameter of drill to be ground. A bore 142 is provided within the drill holder element for accommodating a sleeve 144 havingan internal taper bore 148 for securing frictionally the taper shank of drill 112. Sleeve 144 is smoothly rotative within bore 142, and arranged to be clamped on the sleeve is a rotation limiting device 152, such as is shown and described in the prior application hereinbefore referred to. Thus the limiting device consists of a chuck member 154 having a chuck jaw 156 reciprocal by means of an adjusting screw 158 so as to clamp sleeve 144 within the opening 160. Element 154 is shaped with shoulders 162:1 and 162b for engagement with respective studs 126a and 126b to limit the amount of clockwise and counterclockwise rotation of the limit element 154 to substantially 180 in either direction. When the chuck is clamped to sleeve 144 it provides a handle by means of which the sleeve and drill may be oscillated to bring either lip of the drill into position for grinding engagement with a wheel 166 in a manner explained in detail in my above mentioned prior patent.

The chuck device 152 likewise serves as a means for properly positioning sleeve 144 axially with respect to drill holder element 132 and holding it in that position, a smooth finish engagement between the front surface of holder element 132 and the rear surface of the element 152 being provided so as not to impede rotation.

Thus, in operation of the device, it will be appreciated that as post 66 is rotated counterclockwise to carry the drill towards the wheel 166, a differential grinding of the drill point will occur due to forward sliding of plate 30 plus the eccentric or cam motion provided by the Otfset of post 66. Thus the surface immediately behind the lip will have less material removed therefrom than the surface further back from the lip, yleaving a curved surface from lip to heel instead of a flat surface, and leaving the edge of the lip strongly reinforced by material remaining instead of being ground away as is usually done when drills are ground flat. At the same time proper clearance angle is maintained for the lip, which should be from 12 to 15, depending on the particular layout of the offset or eccentricity of post 66. Each lip of the drill is ground during counterclockwise motion of post 66, the return moti-on of the post serving to remove very little material. The chuck 152 is iipped to engagement with studs 126a and b alternatively at the beginning of each counterclockwise swing.

The action of the two cam motions applies to all sizes of drills in the scope of the machine and will give each size drill the necessary body behind the lips as well as the continuous curve from the point of the drill to the end of the heel.

This causes the drill to cut better and stay sharp longer.

Referring now to Fig. 9, a simplified cradle element is illustrated for accommodating straight shank drills. This cradle element consists merely of the block 170, haw

ing a V-shaped groove 172 to accommodate a straight shank and being adjustably slidable on shaft 116 by means of a tightening screw 174 in a manner which will be well understood. A clamping plate 176 may be utilized to hold element 170 on shaft 116. Limit studs 178a and 173k are provided on side flanges, for the purpose hereinbefore explained for the studs 126a and 126b, and as set forth in my above-mentioned prior patent. This alternative form for the rear element of the drill cradle is furnished as part of a set; thus, when it is desired to grind straight shank drills the rearward cradle element as shown in Fig. l may be removed from shaft 116 and the simple V block 170 substituted thereon, the chuck 152 then being clamped directly to the drill.

By comparing Figs. 5 and 9, it will be apparent that the sides of groove 172 make an angle which is equal to the angle at the bottom of the opening 160. Thus, the V-shaped groove at the bottom of this opening has walls against which the drill body is pressed by means of the clamp element 156. It will be noted that these walls are equal to the angle of the groove 172. Further, it will be noted that the shoulders 162e and 162]: make an angle with each other likewise equal to the angle of the groove 172 and the bottom of the opening 160. In fact, all of the angles in this particular instance equal This is an important point in the construction of the device, since it insures an exact 180 rotation of the drill each time a lip is ground just prior to grinding the other lip.

Referring to Figs. l and la, the relationship of the drill and the grinding wheel 166 is shown, the grinding wheel being provided with a guard 182 to which is fastened an end plate 184 shielding as much of the surface of the wheel as possible. Secured to guard 184 is a bracket 186 which supports a mirror 190 having a scratch line 192 on its surface. It Will be appreciated that when the mirror surface is set at the proper angle with the scratch line disposed at a suitable angle and in fixed position, the post 66 may be swung so that the point of the drill is reflected in the mirror, the axis of the drill then being in a plane normal to the surface of the mirror, although the drill axis itself is not actually normal to the mirror surface. If the lips of the drill, or one lip, is then arranged parallel to the scratch line when either ear 162a or 162b, is engaged with its respective stud 126a or 126b, the setting of the drill will be such that the angle between the lip and the web point will be within a range which is considered suitable with respect to the point of the web for most eicient drilling. Thus, as viewed on Fig. 10, the angle 200 will be within the range of from to this being considered the proper angularity between the point of web 202 and lips 204. It will be appreciated that the exact angle provided is not critical so long as it is within the specified range. The mode of predetermining the particular angularity of the mirror surface and the angle of the scratch line thereacross depends upon the physical design of the combination and can readily be achieved by persons skilled in the art by the use of suitable gauges or by placing a properly ground drill in the fixture and swinging it around to a convenient position in which the reflection of the lips can be readily seen. It should further be noted that the axis of the drill need not be normal to the plane of the mirror, the angle of the mirror being set so as to face upwardly for convenience of the operator. A 45 angle for the plane of the mirror has been found suitable with respect to the horizon while the angularity of the mirror with respect to the axis of the wheel may be set so that a fairly full reflection of the drill point can be effected within the arc of swinging of the post 66.

An alternative method of setting the drill where access is not readily available for a mirror would be by means of an indicia line 210 scratched on the front of element 76, as shown in Fig. 4.

Having thus described my invention, I am aware that many modifications are possible without departing from aihe :spirit 1 thereof and accordingly 1I vfdo-'not u'seek to Ibe `:limited .to the t precise illustration given-herein eexceptfas be .reflectively aligned-withsaid-indiciamark so as `to provide the proper .angle-of -the-drill"-lip-with respect to the grinding surface to-insurepredetermined limits ivf-angu- Ilarity betweensaiddrill -lipand theweb of said'drill.

2. The combinationof-a-grindingwheel, a mirror-having an-indicia-mark-on-the -surfacefthereof in `afpredetermined position, -andadrill-holding fixture having means 'for providing oscillatory lmotion-of-a drill point with re- .spect'to said-wheel,-saidm-irror beingfmounted with Are- :spectto the grinding-surface-of-said'wheel so as to effect .a-.gaugeffor positioning the-lip Iof-afdrill with `respect-to .the indicia mark thereon -whereby -thelip of said-'drill engages the grinding -surface at arf-predetermined --angle i. during oscillatory -motion-w-ith-respect thereto, --said -fixture .beingmovable to -a -degree 4whereatthe axis A'of a drill .thereinmay be'set normalto-the plane of saidmirror.

v3. YThe `combi-nation .of a grinding --whee1, a 'mirror :ad-

jacent the vsurface vthereof, -a Avisible gauge Iline means -manifested on said lmirror in a predetermined fposition, ka'drillholderfsaid drill Vholder being-movableso'that a ,drill carried therein maybe -positionedfto have its Waxisin a plane normal to the mirror whereby a lip of said drill may be refiectively aligned with said gauge line.

4. The combination as set forth in claim 3, said visible gauge line being applied directly on the surface of said mirror.

5. A drill grinding fixture comprising a pivotally oscillatable drill holding means mounted for oscillation in a predetermined plane angularly fixed with relation to the surface of a grinding wheel and means for providing said drill holding means with unidirectional, rectilinear, translational motion in predetermined varying degree toward a grinding wheel during pivotal oscillation of said drill holding means in one direction, said translational motion means being actuated by said oscillation of said drill holding means.

6. A drill grinding fixture comprising a pivotally oscillatable drill support means mounted for oscillation in a predetermined plane angularly fixed with relation to the surface of a grinding wheel and means responsive to oscillation thereof for providing progressively increasing unidirectional, rectilinear, translational, motion of said support means toward a grinding wheel as said means is pivoted in one direction so as to grind off a progressively increasing amount of material rearwardly of the lip of a drill held in said support means.

7. A drill grinding fixture comprising a pivotally oscillatable drill support means mounted for oscillation in a predetermined plane angularly fixed with relation to the surface of a grinding wheel for supporting -a drill so as to grind the drill point against a grinding wheel upon oscillation of said support means in one direction, including means for providing arcuate motion of said support means about an axis offset from the body of a drill held in said support means, and means for providing a simultaneous unidirectional, rectilinear, translational motion of progressively increasing degree to said support means toward said wheel as said support means is oscillated in said one direction, so as to grind off progressively increasing amounts of material rearwardly of a drill lip, said support means having an element for gripping a drill, said element being rotatably reversible Whereby each lip of said drill may be alternately ground in turn.

8. A drill grinding fixture comprising a pivotally oscillatable drill holding means mounted for oscillation in a `predeterminedplane angularly fixed with 'relation to fthe surface Aof Aa grinding wheel and means for providing unidirectional, rectilinear, translational motion Ito a predetermined varying degree of said vdrill holding means ktoward a grinding Wheel vduring oscillation of -saidmeans in .one direction, 'said translational lmotion .being unidirec- 'tional throughout the range of oscillation yin said Aone direction, fwherein said motion providing 'means 'comprises `c-am elements including Ia base, one of said came'lements -oscillatable drill holding means mounted for oscillation in -aipredeterminedplane angularly fixed with relation Vto the surface-of a grinding wheel and means for providing ,unidirectional, rectilinear, translational motion of said drill holding means toward a vgrinding wheel 4responsive to oscillation-of said 'means in one direction, said holding lvmeans having an element for gripping va drill, --sad element being rotatively reversible whereby each lip -of said drill 'Imay be-.alternately ground in turn.

ll. In a-device of theclassdescribed, a support ele- -ment having a trough for supporting at least a portion -ofa=dr'ill, a drill holder adapted Ito be `secured to said drill to serve as a handle for rotating said drill about its axis while it is supported in said support element so as to grind either lip thereof in a rotated position of said drill, said drill holder being formed with an opening, said opening having a pair of converging sides forming a trough in which an intermediate portion of said drill may be accommodated, a clamp element carried by said drill holder for securing said drill fixedly against the sides of said trough to thus clamp said drill in said drill holder, said drill holder having a pair of shoulders having surfaces positioned at a predetermined angle with respect to each other and with respect to the axis of a drill in said holder, and abutment means disposed on opposite sides of said support element alternately engageable by said shoulders to limit rotative motion of said drill holder to either of two stop positions so as to orient one drill lip or the other for grinding, wherein the angle between the sides of said trough in said support element and the angle between the sides of the trough in said holder and the angle between the engageable surfaces of said shoulder are all equal.

l2. In a device as set forth in claim ll wherein said angles are all equal to 13. A drill grinding fixture comprising a drill holding means mounted for rocking about a pivot, said pivot being mounted for rectilinear, translational motion in a plane angularly related to the axis thereof during rocking of said holding means in one direction, and means for effecting said translational motion in varying degree actuated by said rocking of said drill holding means.

14, In a drill grinding fixture as set forth in claim 13, wherein said drill holding means comprises an element for supporting the body of a drill rotatively about the axis of said drill and a chuck operative to be clamped about the body of said drill for selectively rotating said drill to bring one cutting edge or the other into grinding position.

l5. A drill grinding fixture comprising a grinding wheel and a pivotally oscillatable drill holding means mounted for oscillation in a predetermined plane angularly fixed with relation to the surfiace of said grinding wheel, and means for providing said drill holding means with unidirectional, rectilinear, translational motion in predetermined varying degree toward said grinding wheel dur- .ing pivotal oscillation of said drill holding means in one direction, said translational motion means being actuated by said oscillation of said drill holding means.

16. A drill grinding machine comprising a grinding wheel and a pivotally oscillatable drill support means and means responsive to oscillation thereof for providing progressively increasing unidirectional, rectilinear, translational motion of said support means toward said grinding Wheel as said means is pivoted in one direction so as to grind off a progressively increasing amount of material rearwardly of the lip of a drill held in said support means.

17. A drill grinding fixture comprising a grinding wheel and a pivotally oscillatable drill holding means and means for providing unidirectional, rectilinear, translational motion to a predetermined varying degree of said drill holding means toward said grinding wheel dur ing oscillation of said means in one direction, said translational motion being unidirectional throughout the range of oscillation in said one direction, wherein said motion providing means comprises cam elements including a base, one of said cam elements being secured to said oscillatable drill holding means and the other of said cam elements being secured to said base, said cam elements being engageable with each other to actuate said drill holding means responsive to said oscillation in one direction.

18. A drill grinding xture comprising a grinding wheel and a pivotally oscillatable drill holding means and means for providing unidirectional, rectilinear, translational motion of said drill holding means toward said grindingwheel responsive to oscillation of said means in one direction, said holding means having an element for gripping a drill, said element beingrotatively reversible whereby each lip of said drill may be alternately ground in turn.

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